This invention relates generally to protective materials such as bulletproof materials, and more particularly concerns a rigid protective laminate which may be used as a bulletproof shield.
Lightweight protective armour is well-known in the art. For example, Severin U.S. Pat. No. 4,181,768 discloses a laminate useful for body armour comprising alternating layers of Kevlar fabric and 6, 6 nylon film to bind the Kevlar fabric layers into a rigid composite. The bonding process is carried out at temperatures and pressures so that the nylon film only minimally flows into the yarn bundles of the fabric layer. Particularly, the Severin patent discloses a laminate having twelve layers of Kevlar fabric laminated together with eleven internal layers of nylon film and having two external layers of nylon film. The laminate has a thickness varying between 0.242 and 0.265 inch. The area density of the Severin laminate varies from 1.5 to 2.3 pounds per square foot (lb./ft..sup.2). Particularly, in Example of 4 (Item i, Table I), the Severin patent teaches that poor ballistic performance results if the nylon is heated to such an extent that it impregnates the yarn in the Kevlar fabric.
The nylon laminate of Kevlar as disclosed in the Severin patent may be subject to delamination because the nylon does not impregnate the yarn of the Kevlar fabric and thus provide substantial adherence between the layers. Particularly, the presence of moisture which may enter the laminate at the edges is readily absorbed by the nylon, further promoting adhesive failure between the Kevlar layers.